A scientific measure of dog years

How old is your tail-wagging bundle of joy in human years? According to the well-known "rule of paw," one dog year is the equivalent of 7 years. Now, in a study published July 2, in the journal Cell Systems, scientists say it's wrong. Dogs are much older than we think, and researchers devised a more accurate formula to calculate a dog's age based on the chemical changes in the DNA as organisms grow old.